Acrylic is often preferred because of its moderate properties, easy handling and processing, and low cost, but behaves in a brittle manner when loaded, especially under an impact force. Transmits up to 92% of visible light (3 mm thickness), and gives a reflection of about 4% from each of its surfaces on account of its refractive index. It has a density of 1.17-1.20 g/cm3, which is less than half that of glass. It also has good impact strength, higher than both glass and polystyrene.

• Outstanding resistance to long-term exposure to sunlight and weathering.

Acrylic is produced in two basic variations, cast and extruded. Cast acrylic sheet is made to exacting standards. It offers excellent optical characteristics, thickness tolerances, light stability, and low internal stress levels for consistent performance. Extruded acrylic is a continuously manufactured acrylic sheet, resulting in a sheet offering with the easy handling and processing of extruded sheet, along with the high optical characteristics and low stress levels expected of cast products.

Cast acrylic is more difficult to bend and shape versus extruded.

In heat bending and thermoforming, extruded acrylic may behave differently depending on the bending direction relative to the extrusion direction. This is not an issue with cast acrylic. When colored cast acrylic is heated for thermoforming or heat bending, the color may change. Matte-colored surfaces can become clear and clear surfaces can become matte or opaque. In addition, the shade of color may change.

Laser engraving should only be done on cast acrylic to produce a clear engraved image. In laser cutting, extruded acrylic will have a rougher edge, whereas cast is generally smooth.

Cast is more difficult to flame polish versus extruded. Extruded acrylic tends to be more consistent in sheet thickness, while cast can vary as much as +/- 15% in thinner sizes. Cast acrylic is more resistant to the same solvents, as well more resistant to scratching versus extruded.

Acrylic Opacity: Opaque, Translucent and Transparent. What do they mean?

Opacity and transparency both deal with the amount of light that can pass through an object, in this case acrylic plastic.

Opaque Acrylic: Opaque acrylic will let minimal to no light through. An opaque piece of plastic will completely block out light when placed in front of a light source. Opaque acrylics are used in applications where a solid color is desired with no light transmission requirements.

Translucent Acrylic: Acrylics that are translucent allow light through, but with significant diffusion or distortion. Usually allowing in the range of 1% to 50% light transmission, translucent acrylic will allow light through, without showing the object behind. For example, the light from a light bulb will transmit through the acrylic, but the bulb itself will not be visible. A person behind a translucent piece of acrylic may appear as a silhoulette, or not at all, depending on the light transmission percentage. This is contrasted with transparent plastic, where the object behind would be visible with minimal diffusion and distortion.

Transparent Acrylic: Acrylics that are transparent, also referred to as tinted, allow one to see through them as if there’s nothing there. Allowing in the range of 50% to 93% light transmission, images are identifiable just as one would see through a pair of sunglasses. There is a tint, but little to no diffusion or distortion.

Bottom Line: Opaque acrylics let no light through, transparent acrylics let most light through allowing objects behind to be seen, and translucent acrylics allow some light through but with considerable diffusion and distortion.

Physical Properties of Cast Acrylic*

Specific Gravity

1.19

Tensile Strength

10000 psi

Elongation % (Rupture)

4.2%

Flexural Strength (Rupture)

16500 psi

Impact Strength

0.4 lbs/in

Rockwell Hardness

M-94

Light Transmission

92-93%

UV Transmission
(@ 320 Nanometers)

0

Forming Temperature

340-380F

Deflection Temperature
(@ 264psi)

210F

Max Service Temperature

180F

Vicat Softening Point

239F

Self-Ignition Temperature

910F

Dielectric Strength, Short Time

430 volts/mil

Water Absorption
(24 Hours @ 73F)

0.2%

*Values listed are typical and are meant only as a guide to aid in design. Field testing should be performed to find the actual values for your application.

Physical Properties of Extruded Acrylic*

Specific Gravity

1.19

Tensile Strength

10000 psi

Elongation % (Rupture)

4.5%

Flexural Strength (Rupture)

17000 psi

Impact Strength

0.4 lbs/in

Rockwell Hardness

M-93

Light Transmission

92%

UV Transmission
(@ 320 Nanometers)

0

Forming Temperature

300F

Deflection Temperature
(@ 264psi)

195F

Max Service Temperature

160F

Vicat Softening Point

220F

Self-Ignition Temperature

850F

Dielectric Strength, Short Time

430 volts/mil

Water Absorption
(24 Hours @ 73F)

0.2%

*Values listed are typical and are meant only as a guide to aid in design. Field testing should be performed to find the actual values for your application.